Cholesteatoma is a serious otolaryngologic condition that to date remains an important problem and poses a challenge to otolaryngologists around the world. To improve the approach pertaining to the diagnosis and management of middle ear cholesteatoma, clear, clinically applicable, and useful definition and classification of cholesteatoma are required. This review aimed to evaluate the current and most accepted descriptions and opinions concerning cholesteatoma. A review of the literature concerning different definitions and classifications of cholesteatoma was used in the preparation of the Cholesteatoma Guidelines, a project implemented by the European Academy of Otology - Neuro-otology.